Hurrying through a dangerous landscape, the moustachioed plumber comes across unexpected treasure&colon; the furry skin of a raccoon dog, its innards nowhere to be seen. Hastily wrapping the skin around himself – because of course you would do that if you found an animal skin – he develops magical abilities. He can fly by wagging the tail, and transform into a statue at will.

Confused? Don’t be. This happened to many thousands of people in the late 1980s, when they played Super Mario Bros. 3. In this game, Nintendo’s heroic plumber occasionally acquired a “tanooki suit” that gave him exactly these magical abilities.

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In real life, raccoon dogs do not fly or transform into statues. They are not related to raccoons, but they are related to dogs. In fact, they are among the most primitive canids still alive, and the only ones that hibernate.

They are also spreading rapidly. Having spent the last ice age in South Korea, they have now made it as far as Scandinavia.

Tanuki trouble

In Japan, raccoon dogs are known as tanuki, and you often see statues of them outside restaurants – with very large testicles.

On the move

Raccoon dogs were not always so cosmopolitan. Some 20,000 years ago, Earth was in the grip of the last ice age, and raccoon dogs were confined to a small area of east Asia. Mi-Sook Min of Seoul National University in South Korea and colleagues have now examined raccoon dog genes to figure out how their populations have changed.

The team collected 147 raccoon dogs from Korea, Russia, China, Vietnam and Japan, and examined their DNA. The raccoon dogs divided neatly into two groups&colon; one living in Japan, and one living on mainland Asia. That suggests the raccoon dogs survived the ice age by lurking on the Korean peninsula and in Japan. These two groups seem to have been isolated from one another.

The raccoon dog genomes also showed signs of a recent population expansion, suggesting their population had shrunk to a low level and then exploded. It seems that once the ice sheets began to retreat, the raccoon dogs thrived and spread throughout east Asia.

If we had left them to their own devices, they might only now be reaching central Asia. Instead, thanks to the former Soviet Union’s predilection for their fur, they are all the way over in central Europe. And as the climate warms and the ice retreats, they’re only going to spread further.